Method for Determining a Trajectory Representing an Inserting of a Patient Into an MR Scanner

ABSTRACT

A trajectory is determined for inserting a patient into an MR scanner. An avatar representing specific body dimensions is provided. The avatar includes location information relating to an implant. A spatial magnetic field gradient data set relating to the scanner is provided. An avatar pose at a starting point of the trajectory is defined, and a course for the trajectory is provided. For several points on the trajectory, the corresponding magnetic field value are determined by combining the spatial magnetic field gradient data set with the avatar pose. The trajectory and/or the avatar pose are determined so that the at least one implant only passes regions within the MR scanner that are below a predetermined threshold value concerning the magnetic field gradient.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to and the benefit of European patent application no. EP 21215689.7, filed on Dec. 17, 2021, the contents of which are incorporated herein by reference in its entirety.

TECHNICAL FIELD

The disclosure relates to techniques for determining a trajectory for inserting a patient into a magnetic resonance (MR) scanner. The disclosure further relates to a non-transitory computer-readable medium configured to execute a computer program and to a corresponding data processing apparatus.

BACKGROUND

For certain medical purposes, magnetic resonance imaging may be necessary. This can be achieved via an MR scanner. Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to generate images of the anatomy of the physiological processes of the body. Therefore, the corresponding scanners are called MRI-scanners or just MR scanners. Such scanners mostly use strong magnetic field magnitudes higher than the earth's magnetic field. Inside such a scanner using strong magnetic fields, magnetic field radiance and radio waves may be present to generate images of the organs of a body. MR scanners do not involve X-rays or the use of ionizing radiation, which distinguishes it from CT and PET scans. Usually, to perform an MR-scan, the patient is inserted into a gantry of the MR scanner. However, in case of implants like a pacemaker, the procedure of performing the magnetic resonance imaging may become difficult. In such cases, it is relevant whether the implant is considered to be “MR-conditional” or not. MR-conditional is preferably a statement whether patients with certain implants can be scanned in an MR scanner without harming the patient or at least to limit a negative impact to a maximum degree. Commonly, implants that are compatible with MR scanning are labelled “MR safe” or “MR-conditional”.

Manufacturers of an implant can label their products MR-conditional if they perform safety tests on the implants and derive restrictions or limits within which the implant can be scanned safely. Such limits may be, for example, restricted head and whole-body specific absorption rate (SAR) values. SAR values provide information regarding how much energy per unit mass is absorbed when a human body is exposed to a radio frequency (RF) electromagnetic field. For example, mobile phones can be provided with SAR values. SAR values may be averaged over the whole body, or they may relate to a smaller portion thereof such as the head, ear, legs, etc.

SUMMARY

In the case of the MR scanner, a magnetic field is provided for generating magnetic resonance images. The MR scanner provides a static magnetic field, which is often called a B0 field. This magnetic field B0 has the unit of [T/m] (Tesla per meter). The magnetic field B0 can be regarded as “magnetic flux density” with units of T/m. Another expression exists for magnetic field. Instead of magnetic flux density, a magnetic field can be expressed as “magnetic field intensity”, “magnetic field strength”, or “magnetic field”. These expressions are often correlated with “H0” instead of “B0”. These two expressions for the magnetic field are not relevant for this application. They only differ by a constant factor: the magnetic field constant μ0. Whenever B0 is mentioned, this is also true for its corresponding H0 value. The spatial field gradient is preferably the spatial derivative of the static magnetic field B0. Within the imaging volume inside the center of the magnet, the magnetic field B0 is highly homogeneous. Outside of the imaging volume, the magnetic field usually first rises and then may drop to zero. An exact shape of the magnetic field depends on the magnet design and varies with each scanner type. The examination space is usually related to the gantry of the MR scanner and is mostly inside the MR scanner. The spatial field gradient may be provided by the MR-manufacturer via field plots.

Magnetic resonance imaging may become difficult or problematic in the case of implants that contain ferromagnetic materials, or active devices in which the field changes while they are passing through the gantry, inducing currents. Since the magnetic field varies along a path on which a patient is inserted into the MR scanner, the interaction of the ferromagnetic material of the implant and the magnetic field or the magnetic field gradient may cause forces and torques. Ferromagnetic materials may be e.g. iron, cobalt, nickel, dysprosium, holmium, or erbium. Although manufacturers of implants try to avoid ferromagnetic materials by using alternative materials such as titanium, in rare cases ferromagnetic or even magnetic materials are necessary to be used within implants. For example, in such cases manufacturers may limit the maximum spatial field gradient exposed to their implants to a value which guarantees a safe handling and scanning in the environment of an MR scanner.

If a patient has an implant with a ferromagnetic material, the scanner operator has to research all MR-conditional limits before the scan can be started. The operator has to make sure that during the scanning process the provided limits of the manufacturer are not exceeded. The operator is reliant on information from the manufacturer of the MR scanner and the manufacturer of the implant. For example, the manufacturer of the MR scanner can provide field plots representing the magnetic field inside and around the MR scanner. Usually, the operator has to figure out whether and how to insert the patient into a specific MR scanner. This procedure may be complicated and inconvenient.

Therefore, a task of this disclosure is to support the operator in determining a trajectory or a pose for safely inserting a patient into an MR scanner. For example, the operator can be supported by determining a pose for the patient for inserting him into the MR scanner.

This task may be achieved by the embodiments as described throughout the disclosure, including the claims. Additional advantageous embodiments are provided by the Figures.

A first aspect of this disclosure provides a method for determining a trajectory for inserting a patient into a given MR scanner. This method can be carried out by a computer. This means that this disclosure can be regarded as a computer-implemented disclosure (e.g. a computer-implemented method). In many embodiments described herein it is possible to perform the disclosure or the embodiments via a computer without an MR scanner. Other embodiments include the MR scanner. The method includes the following steps:

In step a) an avatar representing specific body dimensions of a predetermined patient is provided, wherein the avatar includes location information relating to at least one implant. The avatar may be a model, an electronic data set, or a data set that contains the specific body dimensions of the predetermined patient. This means that the avatar may be regarded as a non-physical object. The avatar may be a simple two-dimensional model or even a detailed three-dimensional model of the body of the predetermined patient. The avatar may be focused on the outer body dimensions of the patient. The avatar may already include location information of the at least one implant. Such location information may remain within the body dimensions of the patient, since the implant is usually located inside the patient's body or at least attached at the body of the patient. This results in implant location information that is inside the avatar and/or within the body dimensions being represented by the avatar. The location information may be combined with the avatar beforehand. The avatar may be provided by combining or fusing the specific body dimensions of the patient with the location information relating to the at least one implant. The predetermined patient may be e.g. the person to be examined via the MR scanner.

In the next step b) a spatial magnetic field gradient data set is provided relating to the MR scanner. This spatial magnetic field gradient data set may describe a magnetic field and/or the magnetic field gradient that is induced by the MR scanner. This data set may comprise magnetic field values and/or magnetic field gradient values. This means that the spatial magnetic field gradient data set can comprise magnetic values, which may refer to a position or location relative to the MR scanner. It is possible that the spatial magnetic field gradient data set can comprise magnetic field data in the form of magnetic field values together with position information relative to the MR scanner. For example, the data set can comprise contour lines representing constant magnetic field values. Different contour lines may relate to different magnetic field values. Whenever the expression “magnetic field value” is used, this expression may refer to magnetic field value and/or to its gradient value. It may depend on the information provided by the manufacturer. The spatial magnetic field gradient may be provided by the manufacturer of the MR scanner.

In the next step c) an avatar pose is defined as a starting point of the trajectory and a course for the trajectory is defined for inserting the patient into the MR scanner. This means that the positioning of the patient may be defined before he will be inserted into the MR scanner. The avatar pose may contain information about the position of extremities of the patient, such as hands, the head, or the legs of the patient together with their orientation. This means that the avatar pose may contain information about the position and orientation of several corresponding extremities. The extremities of the patient may be his head, hands, fingers, and/or legs. The avatar pose may contain the information whether it is the legs or the head of the patient that will enter the gantry first. Furthermore, the avatar pose may contain the information whether the patient is lying on her back, on her stomach, or on her side. This means that the avatar pose can provide an exact information or instruction as to how the patient needs to be positioned for insertion into the MR scanner. Furthermore, a course for the corresponding trajectory may also be defined. In this simple case, the trajectory may be defined by a horizontal line that remains constant. In this case, the course for the trajectory may represent a horizontal movement of the implant into the gantry of the MR scanner. The trajectory may refer to the at least one implant. In most cases, the pose of the at least one implant remains constant throughout the trajectory. But in certain cases, it may be advantageous to perform a change in the pose of the implant inside the MR scanner or a movement with a vertical component to avoid critical regions inside the MR scanner. Such movement may be necessary if the implant would enter regions where the magnetic field value is larger than suggested by the manufacturer of the implant. These regions may be regarded as “critical regions”. Each individual implant may be identified with its own critical regions.

The critical regions may be gathered by combining information from the implant manufacturer and a “magnetic field map” provided by the scanner manufacturer. The critical regions can be determined by a fused database that includes the spatial magnetic field gradient data set, the defined avatar pose, and the course of an envisaged trajectory for inserting the patient into the MR scanner. Each node or position of such a fused database that exceeds a predetermined threshold value with regard to the magnetic field gradient may be classified as a critical region on the trajectory. It is possible to only determine where inside the MR scanner the magnetic field gradient is higher than the threshold value to identify critical regions. Ideally, the trajectory does not enter any critical region.

In a next step d) the corresponding magnetic field value and/or its gradient may be determined for several points on the trajectory. This can be achieved by combining the spatial magnetic field gradient data set with the avatar pose. It is possible to combine the spatial magnetic field gradient with the avatar pose and additionally with the defined trajectory. This means that the spatial magnetic field gradient data set, the avatar pose, and the defined trajectory may be combined and/or fused into a new data set. With this new data set it is possible to determine and/or to adapt the trajectory.

In a next step e) the trajectory and/or the avatar pose can be determined and/or adapted so that the at least one implant only passes regions within the MR scanner data below a predetermined threshold value concerning the magnetic field gradient and/or its gradient value. This can be achieved for example by comparing the magnetic field values for several points on the trajectory with the provided threshold value. The provided threshold value may be gathered or derived from manufacturer information of the implant.

This step may be conducted iteratively. This means that, in case a trajectory passes regions exceeding the threshold value, another trajectory and/or pose of the avatar may be defined and the corresponding magnetic values on the trajectory may again be compared with the threshold value. This step can be performed as a regulation loop. This means that the avatar pose and/or the trajectory can be modified several times until a trajectory is determined that only passes regions within the MR scanner data below the threshold value concerning the magnetic field gradient. This regulation loop can be continued until, for each implant, a trajectory is determined in which no critical regions are encountered during a later inserting procedure.

In a next step f) an information signal can be generated that indicates whether the determined trajectory guides the at least one implant in such a way that it enters regions exceeding the predetermined threshold value. For example, the information signal may visualize the determined trajectory. For example, critical regions where the magnetic field value or its gradient exceeds the threshold value can be visually highlighted. A red blinking e.g. is possible in this context. Step f) may be regarded as a feedback provided as to whether the determined trajectory can be safely applied to insert the patient into the MR scanner. This means that the operator of the MR scanner can be provided with detailed information as to how to position and/or to insert the patient into the MR scanner. This method can guarantee a safe handling if the patient is examined inside the MR scanner. Since an optimal avatar pose and/or trajectory can be determined, unpleasant or even painful forces or torques on the implant can be minimized or even avoided. Furthermore, it is possible that by use of this method, preparation procedures for the operator can be accelerated.

According to an additional or alternative embodiment, it is possible that the trajectory is determined several times iteratively until, for each implant, a trajectory is determined which does not enter regions exceeding the magnetic field gradient. This means that in case no optimal trajectory is determined, a further process for determining the trajectory is conducted. In such a situation, a new trajectory is defined or calculated by adapting the avatar pose and/or the course of the trajectory. The trajectory may describe a path of the avatar that is moved into the gantry of the MR scanner. For all determination processes, it is possible that several predetermined points on the trajectory are analyzed as to whether their corresponding magnetic field value exceeds the corresponding threshold value. A control unit may calculate a different avatar pose and/or a different trajectory for the process of iteratively determining the trajectory. This process can be proceeded as long as a trajectory is calculated that does not enter a critical region, where at least one implant enters a region within the MR scanner with magnetic value that exceeds its corresponding threshold value. It is possible that the operator can define different avatar poses and/or trajectories for iteratively determining the trajectory. Different avatar poses and/or trajectories for the at least one implant can be provided for iteratively determining a final pose and trajectory. For instance, the trajectory may contain the avatar pose and the course of the at least one implant. The avatar pose may be necessary for determining the trajectory. Since the MR scanner is limited in terms of its dimensions, especially the gantry of the MR scanner, possible trajectories for the implant may depend on the body dimensions of the patient and the dimensions of the gantry of the MR scanner. These dependencies may be considered for determining and/or adapting the trajectory in step e). Therefore, an optimal or final trajectory may be evaluated or found by iteratively determining the trajectory.

An additional or alternative embodiment allows for a set of several separate trajectories to be determined for each implant. In this embodiment, the avatar comprises location information of several implants and a set of several separate trajectories is determined for each implant. Each trajectory relates to a corresponding implant and, for each individual implant, a separate threshold value can be applied. For example, a patient may have several implants. It is possible that the patient has a pacemaker, an artificial hip, a knee joint, and/or an artificial limb. For example, if the patient has two different implants, two trajectories can be determined for these two implants. Each trajectory may be related or assigned to an individual implant. The number of trajectories can be the same as the number of implants. This means the implants and the corresponding trajectories can define a bijective relation (i.e. a one-to-one correspondence). In this case, each implant is related to exactly one trajectory. The threshold value for each individual implant may be different according to the recommendation of the manufacturer. In this embodiment, the control unit may be configured to determine those trajectories that remain below their corresponding magnetic threshold values and are possible to realize. This means that the several trajectories cannot be treated independently, since their positions within the avatar may underlie some restrictions. For example, the position of the pacemaker of a patient cannot be changed in a way so that a distance from the patient's head can be significantly increased. Due to the anatomy of the patient, some restrictions may arise. Nevertheless, due to the flexibility of the extremities, there remains some degree of freedom to adapt the trajectories for the two implants independently. This concept can be extended analogously to more than two implants.

In certain embodiments, it may be possible that a situation arises in which no set of appropriate trajectories can be determined, and all trajectories pass regions within the MR scanner that are above the corresponding threshold value concerning the magnetic field gradient value. This means that at least one trajectory would enter the so-called critical region, where the implant would pass a position within the MR scanner where the magnetic field value exceeds its threshold value. A warning signal may be provided in this situation. The warning signal may indicate that it is not possible to insert the patient into the gantry of the MR scanner so that every critical region for the implants can be avoided. In such a situation, an evaluation may be performed. This means that the set of trajectories is selected that would cause the lowest drawback for the patient. Usually, the operator decides which trajectories are applied for inserting the patient into the gantry of the MR scanner. Although this situation is not desirable, it may be advantageous that the operator can be informed about this situation. On the basis of this result, the operator can evaluate whether and how the patient can be inserted into the gantry of the MR scanner.

An additional or alternative embodiment allows for determining the trajectory in a coordinate system with regard to the MR scanner. This means that for determining the trajectory, a coordinate system with regard to the MR scanner is applied and one coordinate of the coordinate system represents an insertion depth. The coordinate system may indicate a position relative to the MR scanner. For example, an x axis may represent a table for the patient. A z-axis perpendicular to the x axis may represent a vertical extension of the gantry. A y-axis may represent a further extension of the gantry perpendicular to the vertical extension of the gantry. The z-axis is often to be considered as a direction identified with a table on which the patient is located. A control unit of a computer or the control unit of the

MR scanner is configured to perform any coordinate transformation for determining the trajectory. The control unit is configured to calculate, from the given information by the avatar, the relative position of the implant to the patient table. In this embodiment, the patient table would represent (i.e. be aligned with) the x-axis. By assuming the table moves into the gantry and the avatar remains still, all positions of the implant can be calculated and located during the table motion. For this purpose, constant velocity of the table motion can be considered. It is possible to consider the velocity of the patient table moving into the gantry for evaluating possible interactions between the implant and the magnetic field inside the MR scanner. By using an appropriate coordinate system, it may be easier for the operator to follow and deconstruct the determined trajectory.

An additional or alternative embodiment allows for the avatar to comprise the pose of the patient and the at least one implant. In this embodiment, the trajectory can be determined considering a maximum insertion depth and the pose. The avatar may not only show a rough structure of the extremities of the patient, but may further comprise pose information of several individual extremities of the patient. Since the avatar also contains location information concerning the at least one implant, a penetration depth of the implant into the gantry of the MR scanner can be calculated. The penetration depth can be determined depending on the maximum insertion depth. The determining of the trajectory may depend on the maximum insertion depth and/or the penetration depth of the at least one implant. For example, if a patient shall be inserted with his feet first and a maximum insertion depth is 0.5 m, a pacemaker would not reach any critical regions where the magnetic field value exceeds the corresponding threshold value.

Another additional or alternative embodiment allows for adapting the trajectory. In this embodiment, the pose of the avatar can be determined for a starting point of the trajectory by one or more images of the patient at the starting point. This embodiment can be combined with the iterative determining of the trajectory. Whenever another trajectory shall be determined, it is possible to advise the patient to move into another pose. The same is possible with the avatar data set or with a real physical “dummy” avatar. With the help of one or more images, it is possible to determine a new pose for the avatar and/or the patient. The new pose of the patient or avatar can be determined by image (e.g. machine) vision, for example. This new pose can be considered by the avatar and, by an appropriate adapting of the avatar, a new trajectory can be determined. This means that a different pose of the patient leads to an adapted trajectory for inserting the patient into the MR scanner.

Another additional or alternative embodiment allows that the avatar is provided by a camera, a first sensor configured to measure the dimensions of the patient, and/or a second sensor configured to measure the weight of the patient. The camera is configured to measure the dimensions of the extremities of the patient. These may be his head, arms, hands, fingers, legs, feet, etc. These dimensions may be approximated by simple geometric models such as ellipses, rectangles, circles, and/or squares. With the help of image vision technology such as optical flow, it is possible to measure the corresponding dimensions. Moreover, with a scale, it is possible to measure the weight of the patient. Based on this information, a possible sink effect of the patient table that is used to insert the patient into the MR scanner can be predicted. This sink effect can be considered for determining a trajectory. For example, for a patient whose weight is double than usual, a different offset value for the trajectory can be considered.

By using the camera, the first sensor, and second sensor, the process for determining and/or adapting the trajectory can be enhanced or accelerated. A further additional or alternative embodiment allows to provide a three-dimensional avatar. The three-dimensional avatar is a model or data set that contains three-dimensional information. In simple use cases, the avatar may be approximated by two-dimensional models. With regard to this embodiment, the avatar is three-dimensional. The three-dimensional information also extends to the implant. This means that the location information of the at least one implant in the avatar model also comprises three-dimensional information.

The 3D avatar can be provided by a three-dimensional camera, an MRI-scan, a Magnetic Resonance Tomography (MRT)-scan and/or a computerized tomography (CT)-scan, etc. In case of a CT-scan, the data are extracted by the use of X-rays. The MRI-scan or MRT-scan relate to magnetic resonance imaging or magnetic resonance tomography. Any available data or model can be applied to generate the three-dimensional avatar. Therefore, previously conducted MRI-scans and/or the CT-scans can be used. The informational data from these previously-conducted scans can be fused to the three-dimensional avatar. For instance, the 3D-camera can extract a three-dimensional avatar representing the specific body dimensions of the patient.

A further additional or alternative embodiment comprises determining a three-dimensional trajectory. In this embodiment, a three-dimensional trajectory is determined and at least one point corresponding to the implant changes vertically along the trajectory. This means that in case of a coordinate system where the x-axis represents an insertion depth into the gantry of the MR scanner, the trajectory shows a movement that is vertical to this x-axis. The expression vertical relates to an upward direction that is perpendicular to the insertion depth. Such a vertical movement may be achieved for example by an appropriate lifting device. The lifting device may for example be a lifting ramp, a lifting platform, or any suitable electric or other hydraulic device that is configured to lift at least a part of the patient's body, or a pillow with the part of the patient's body, on it. This allows for influencing the trajectory directly by the lifting device. An entering of the at least one implant into a critical region may be avoided and/or an improved trajectory and/or pose can be determined. This approach may be useful if a certain position within the MR scanner is to be avoided. This embodiment may be particularly useful if a critical region is encountered during the procedure of inserting the patient into the MR scanner. After lifting the implant over this critical region, a stationary position of the avatar or patient may be reached. In this position, an MR-scan can be performed, and the implant could be lifted over the critical region.

Another additional or alternative embodiment allows that the avatar is fused with provided data relating to the at least one implant. For instance, this additional data relating to the at least one implant can be provided by an X-ray photograph, an MRI-image, a CT-image and/or other data sources such as information from a patient file. It is also possible to approximate the avatar by a rectangular model. Such an approach may be sufficient in many cases. Whenever a higher degree of precision is necessary, information provided by X-ray photographs, MRI-images, or CT-images can be used. This information can be fused with the avatar to create an improved avatar model. Previously acquired MRI-scans, X-ray photographs and/or CT scans can hold the additionally advantage of having improved information about the implant and/or its position inside the patient. Thus, the trajectory can be determined and/or adapted with more accuracy.

For example, the localization of the implant in the avatar can be performed by cross-sections from various perspectives. Different cross-sections may be extracted from a three-dimensional avatar. The at least one implant may be localized during a patient registration. This means that the implant can be localized before the patient may be positioned on the patient table. A localized implant with regard to the body of the patient may be transformed automatically into the avatar. The avatar can be created from a camera or a three-dimensional camera. This means that the camera or the 3D camera may create an appropriate avatar model, and as a further data set or localization information the position of the at least one implant can be translated into the model or coordinate system representing the avatar. It is also possible that the control unit or a computer can detect and/or receive information concerning the size of the implant so that the dimensions of the implant can be included in the model representing the avatar.

A further additional or alternative embodiment allows that the spatial magnetic field gradient data set and the trajectory are fused to provide a new magnetic path data set. All necessary information for determining and/or adapting the trajectory may be combined in a single data set. This means that this single data set may contain information about the pose of the avatar, the course of the trajectory, the corresponding magnetic field values on the trajectory, information about the implant especially a type and ferromagnetic material of the implant, dimensions of the gantry of the MR scanner and/or the pose of each implant with regards to the avatar, etc. By creating one single data set that contains all relevant information for determining the trajectory, the process for the determination or calculation may be simplified or accelerated.

Another additional or alternative embodiment allows that the location information of the at least one implant is approximated by one or more planar areas or volumes that completely contain the at least one implant. The planar areas or volumes may indicate the position of the implant inside the avatar that represents the body dimensions of the patient. This approximation can be combined with a camera that creates a simplified two-dimensional model of the patient. In this case, significant extremities of the patient may be approximated by appropriate rectangles. Additionally, it is possible to increase the planar area or volume by a certain safety margin. This allows for considering errors or deviation for the implant localization.

A further additional or alternative embodiment allows to determine positioning instructions for adapting the trajectory according to step e). This means that for determining and/or adapting the trajectory positioning instructions can be provided. With these positioning instructions the operator and/or the patient can be supported in positioning the patient and thus the implant correctly by indicating how the patient needs to be moved on the table for a safe movement into the scanning position inside the MR scanner. For this purpose, software or the control unit may be configured to help the operator or patient to position the patient and the corresponding implant correctly by e.g. acoustic instructions and/or by using an optical indication for the patient. For example, available screens at the side of the gantry can show instructions for the patient, e.g. how she should move or position herself. Such acoustic instructions may be e.g. “please move the patient five centimeters to the right”.

Inside the gantry, visual markers may help the patient to keep in the correct pose. Additionally, by means of visual arrows or cues, the operator and/or patient can be supported in positioning the patient. Visual cues may be a live view of their body on the table provided by the camera accompanied with a red or green light. By means of an appropriate arrow, the direction to move the patient into a correct position can be indicated. The positioning instructions may be e.g. determined after an optimal trajectory is determined. The positioning instructions may rely on the determined trajectories.

In a further additional or alternative embodiment, the trajectory relates to a course of the at least one implant, where in the case of several trajectories, each trajectory is assigned to an individual implant. Each trajectory can be connected with the appropriate individual implant. The assignment between the trajectories and the individual implants may be bijective (i.e. a one to one correspondence).

Another additional or alternative embodiment allows for the determination of the trajectory of the implant depending on the body dimensions gathered from the avatar and given gantry dimensions of the MR scanner. This means that the trajectory is determined considering the body dimensions of the patient and the given gantry dimensions of the MR scanner. The body dimensions gathered from the avatar represent the body dimensions of the patient to be examined. This may lead to the result that not all automatically possible trajectories are actually possible in reality. Due to the body dimensions from the avatar and the gantry dimensions, some mathematically possible trajectories may become impossible or unrealistic. This embodiment can ensure that only meaningful trajectories are determined.

A second aspect of this disclosure relates to a computer program and/or a control unit. The computer program and/or control unit comprise instructions which, when executed by a computer or the control unit, cause the computer and/or control unit to carry out the method of any of the embodiments mentioned in the disclosure. The computer program may comprise a control unit and/or a microprocessor. The computer program may be realized as a computer program product. The control unit can collect all necessary information for determining the trajectory by appropriate interfaces. With the information such as the avatar model, the data of the MR scanner, and the position of the implant inside the avatar, the control unit is able to determine the ideal pose and trajectory for the avatar.

The control unit may comprise one or more microprocessors and/or one or more microcontrollers. Further, the control unit may comprise program code that is configured to perform any method or any embodiment mentioned in this application when executed by the control unit. The program code may be stored in a data storage of the control unit or in any suitable location accessible by the control unit.

The control unit can comprise a processor configured to perform the method of any embodiment or example mentioned in this disclosure. The control unit can be realized by a computer program product or a data processing apparatus with the control unit comprising instructions which, when executed by the computer or the control unit, cause the control unit or computer to carry out any steps of all embodiments or methods mentioned within this disclosure. The computer program can comprise instructions which, when executed by the control unit or the computer, cause the control unit to carry out or execute the steps of any embodiment mentioned in this disclosure.

Furthermore, according to a third aspect of this disclosure, a computer-readable medium, on which the computer program is stored, is provided.

A fourth aspect of this disclosure relates to a data processing apparatus. The data processing apparatus may comprise an MR scanner. The MR scanner comprises an insertion tool configured to insert a patient into the MR scanner. The insertion tool may be the patient table, for example. Moreover, the data processing apparatus can comprise an interface to receive and/or to gather an avatar (e.g. data identified with the avatar) representing body dimensions of the patient. The avatar may include location information with regard to at least one implant. The at least one implant preferably is located within the body dimensions.

Furthermore, the interface is configured to receive and/or to gather a spatial magnetic field gradient data set with regard to the MR scanner. Such a data set can be provided as field plots in several planes of perpendicular orientation. The data processing apparatus may e.g. comprise a control unit configured to perform any one of the mentioned embodiments in this disclosure. This means that the control unit can cause signals and/or instructions on a computer so that the described methods herein are realized. If all relevant data are combined or fused to render a single data set, it is possible to conduct the method on a computer. The computer can generate control signals to perform a movement of the patient into the MR scanner. All mentioned examples, features, and advantages for the methods analogously apply for the data processing apparatus.

An additional or alternative embodiment of the data processing apparatus comprises a camera for the MR scanner. In this embodiment, the control unit is configured to consider a detected movement inside the MR scanner for determining and/or evaluating the at least one trajectory. By means of the camera, the control unit is able to check the position of the patient inside the gantry or bore of the MR scanner. Thereby, a detected movement of the patient can be compared with an appropriate threshold value concerning the movement. In the case of a detected movement, the control unit is configured to evaluate whether a scanning process inside the gantry should be continued. For example, the control unit may recalculate the trajectory considering the detected movement of the patient. Since the trajectory relates to the at least one implant, any detected movement of a body part without implant may be neglected.

A recalculation of the trajectory may become necessary if the detected movement results in an appropriate movement of the at least one implant. This means that the control unit can provide an instant live (e.g. dynamic and/or real-time) recalculation of the trajectory inside the MR scanner. By considering the detected movement inside the MR scanner, a new trajectory can be calculated. Furthermore, this trajectory may be evaluated if the trajectory enters a critical region. In such a situation, the operator can decide whether the scanning will be continued or the patient has to move appropriately in order to continue the scanning

A further alternative or additional embodiment for the data processing apparatus comprises a lifting device that is configured to lift and/or to lower at least a part of the patient's body to perform a vertical movement of an implant of the patient. The lifting device may be applied during the movement of the patient inside the gantry. A lifting device may be a simple pillow, or any suitable hydraulic or electric platform that is able to lift or to lower at least a part of the patient's body. Thus, a movement of the at least one implant can be induced. During the procedure of inserting the patient into the gantry the trajectory of the implant may bypass critical regions where the magnetic field values exceed the threshold value.

The features, examples, and advantages presented in connection with the method according to the first aspect of the disclosure, with the computer program according to the second aspect, and with the computer readable medium according to the third aspect apply mutatis mutandis to the data processing apparatus according to the fourth aspect of the disclosure, and vice-versa. This means that features of the method or the computer program can be considered to be features of the data processing apparatus and/or control unit. Inversely, features of the data processing apparatus may be considered to be features of the method for determining the trajectory.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure is further described by the following figures. The figures only exemplarily show how the disclosure can possibly be realized. All mentioned features relating to the figures can be extracted and combined with the embodiments mentioned in this implication. The following figures show:

FIG. 1 illustrates an example schematic front cover view of an MR scanner in accordance with one or more embodiments of the present disclosure;

FIG. 2 illustrates an example vertical section through the scanner in a side view in accordance with one or more embodiments of the present disclosure;

FIG. 3 illustrates an example top view of a horizontal section through the scanner in accordance with one or more embodiments of the present disclosure;

FIG. 4 illustrates an example field plot indicating magnetic field values inside the MR scanner in accordance with one or more embodiments of the present disclosure;

FIG. 5 illustrates an example schematic overview of a data processing apparatus in accordance with one or more embodiments of the present disclosure;

FIG. 6 illustrates an example schematic flow diagram representing an example of conducting a method of this disclosure in accordance with one or more embodiments of the present disclosure.

DETAILED DESCRIPTION OF THE DISCLOSURE

FIGS. 1-3 show different exemplary views of an MR scanner 11. In FIG. 1 , a front cover view of the MR scanner 11 is shown. A gantry 10 is indicated by a double arrow. The gantry 10 is the opening through which a patient 27 is inserted into the MR scanner 11. Some MR scanners 11 are provided with information concerning critical regions 21. In FIG. 1 , the critical region 21 is illustrated by an ellipse on the left side of the gantry 10. In these critical regions 21, a spatial gradient value may be present that may be harmful with respect to an implant 25 (see FIG. 2 ). The MR scanner 11 may be in connection with (e.g. communicatively coupled with) a control unit 15 (e.g. control circuitry). The control unit 15 may be realized by a computer, a microprocessor, processing circuitry, etc. Nevertheless, the method can be performed without the MR scanner 11 if all necessary data are provided beforehand. This means that determining or calculating a trajectory 23 may be conducted before the patient 27 will be inserted into the gantry 10. Determining the trajectory 23 may be performed remotely on a separate computer. The so-determined trajectory 23 may be transmitted to the MR scanner 11 via an appropriate interface 30. FIG. 5 shows an overview of a possible data processing apparatus 100. The MR scanner 11 is driven by a magnetic field that is regarded as a “field of the gradient system” B1. The field of the gradient system B1 is applied around the gantry 10, and is not the same as the magnetic field gradient B0 that is present inside the MR scanner 11 in the gantry tube. For this disclosure, the field of the gradient system B1 is of minor relevance.

FIG. 2 shows the magnetic field B0 together with an avatar 22 inside the MR scanner 11. In FIG. 2 , a vertical section through the scanner is shown in a side view. In FIG. 2 , the avatar 22 is indicated together with the implant 25. The implant 25 can be e.g. a pacemaker. The avatar 22 may be regarded as a model or a data set that represents the body dimensions of the patient 27. In most cases, it is sufficient if the avatar 22 approximates the extremities of the patient 27. The patient's extremities are his torso, head, arms, and legs. In many cases, such an approximation is precise enough to determine the appropriate trajectory 23.

In FIG. 2 , a starting point 23 s is indicated. The starting point 23 s is outside the MR scanner 11. FIG. 2 shows a camera 14, which allows for the detection of any movement inside the gantry tent. In case a movement of the patient 27 is detected, it can be registered by the control unit 15. If the control unit 15 detects a movement of the patient 27 inside the MR scanner 11, the control unit 15 can dynamically (e.g. instantly, excepting for system latency) recalculate the trajectory 23. If the recalculated trajectory 23 would enter a region inside the MR scanner 11 which exceeds a defined threshold value concerning the magnetic field gradient value B0, an appropriate warning signal may be provided.

FIG. 3 shows a top view in a horizontal section through the scanner 11. The avatar 22 can be a model or data set relating to the MR scanner 11. Since the patient 27 usually lies on a patient table 13, a determining or calculating of the trajectory 23 can be based on the patient table position. The MR scanner 11 can comprise a lifting device 29. The lifting device 29 allows for an active influence on the trajectory 23 of the implant 25. For example, the lifting device 29 can be a hydraulic platform. A part of the patient's body such as a leg can be lifted and lowered. The lifting device can also be used as a blocking element. Therefore, it can be avoided that the trajectory 23 enters any critical regions 21. This allows for a bypass of the implant 25 with regard to critical regions 21.

In FIG. 4 , an exemplary field plot is presented. This field plot shows areas within the gantry 10 that are related to different magnetic field values B0. Above the gantry 10, the field of the gradient systems B1 is indicated that drives the MR scanner 11. Areas with the same magnetic field values B0 are shown by contour lines 20. The x-axis represents a direction of the patient table 13. The z-axis represents the vertical direction perpendicular to the patient table 13. The z-axis may be a vertical (i.e. upward) direction with respect to the patient table 13. As can be seen from FIG. 4 , the magnetic field values B0 vary from 0.1 Tesla per meter up to 6 Tesla per meter. The gray region in the z-direction between 0.4 and 1.1 represents an area with a nearly homogenous magnetic field B0.

A critical region 21 is indicated in FIG. 4 . In this position, the magnetic field value B0 is 6 Tesla per meter. If the implant 25 is not to enter a region where the magnetic field value is larger than 3 Tesla per meter, the trajectory 23 has to be calculated or determined so that the trajectory 23 bypasses such critical areas 21.

In FIG. 4 , two exemplary trajectories 23 are indicated. These two exemplary trajectories 23 have two endpoints 24. The endpoints 24 relate to a maximum insertion depth of the patient 27 into the gantry 10. Any spatial change in the magnetic field B0 and hence a resulting spatial field gradient can cause forces and torques on ferromagnetic materials. Iron for example is a ferromagnetic material.

Again, although many implants 25 are constructed without ferromagnetic materials, in some cases it is necessary to use such ferromagnetic materials for implants 25. In such situations, it is necessary to determine or calculate the trajectory 23 that does not enter any critical regions 21. Usually implant manufacturers try to avoid ferromagnetic materials by using alternative materials such as titanium. However, in rare cases ferromagnetic or even magnetic materials have to be used within implants 25. In this case, a maximum spatial field gradient is provided together with the implant 25 by the manufacturer. These limits shall guarantee a safe handling and scanning in the environment of an MR scanner 11.

This situation may lead to a quite complicated workflow for an operator of the MR scanner 11. At first, the operator has to research all magnetic field value B0 limits for the implants 25 inside or at the patient 27. The operator has to make sure that the MR scanner 11 will not exceed these limits during the whole examination of the patient 27. It should be considered that the operator has to consider multiple limits. For example, the operator has to consider a SAR value. The operator further has to consider an additional magnetic field B0 that results during the scanning process while the patient 27 is still resting inside the gantry 10. With regard to the additional magnetic field that is only relevant during the scanning process, only the end position and pose of the patient 27 at the endpoint 24 is of importance. In this case, the control unit 15 may also consider or determine an avatar pose at the endpoint 24. This avatar pose at the endpoint 24 represents the pose of the patient 27 when he has reached his end position in the endpoint 24.

The trajectories 23 presented in FIG. 4 may not be the final trajectories. It is possible that these trajectories represent intermediate trajectories during an iterative determining of a final trajectory 23. The operator can define another trajectory 23, and the control unit 15 can determine whether such trajectory would guide the implant 25 in such a way that it does not enter any critical regions. Again, a critical region is a region where the magnetic field value or its gradient exceeds a certain threshold value, which is often defined by the manufacturer of the implant 25.

The magnetic field B0 inside the gantry 10 and around is mostly not constant in all regions inside the scanner 11. The name spatial field gradient already indicates that the magnetic field values B0 may vary inside the scanner 11. In some areas, the magnetic field B0 may vary spatially so much that it could harm the patient 27 with certain implants 25. Usually, the operator has to find out all volumes which may exceed a predetermined limit and then handle the patient 27 in such a way that the implant 25 never enters these volumes. This means that the implant 25 should never enter a volume around the critical regions 21.

It is important to note that the positioning of the patient 27 on the table 13 may significantly define how the implant 25 proceeds into the bore or gantry 10. This means that the pose of the patient 27 at the starting point 23 s significantly influences the trajectory 23 for the implant 25. The pose of the patient 27 can be represented by the pose of the avatar 22. Since the avatar 22 represents the body dimensions of the patient 27, a pose of the avatar 22 can be regarded as a pose of the patient 27. The pose may consider the position and orientation of all extremities of the patient 27. The extremity that contains the implant 25 is of significant relevance.

For instance, in the case of a pacemaker, the focus for determining the trajectory 23 is on the torso of the patient's body. A certain pose for the avatar 22 is defined for the patient 27, and the patient table 13 moves along the x axis as indicated in FIG. 4 . The control unit is able to determine or calculate the corresponding trajectory 23. Conventionally, the operator has to figure out the right or appropriate pose for the patient 27 on his own. In many cases, the critical regions 21 are rings around the bore entry so that the operator has to position the patient 27 with the implant 25 close to the center axis of the magnet.

In practice, some obstacles may arise concerning the insertion of the patient 27 into the gantry 10. For example, most of the MR scanner operators do not know what the spatial field gradient is. MR-physicists usually have this knowledge, but technical and radiological people often do not have this knowledge. In many cases, the spatial field gradient is associated with the field of the gradient system. These two expressions sound similar, but in fact relate to different aspects. The field of the gradient system relates to a patient 27 without any motion during scanning in the scanner 11. The field of the gradient system is usually not relevant for determining the trajectory 23. The spatial field gradient, on the other hand, is relevant for determining the trajectory 23. If the operator mistakes these two aspects, it may be possible that the process of inserting the patient 27 into the gantry 10 relies on incorrect facts. Spatial field gradients are usually given by the MR scanner manufacturers in the form of field plots, e.g. as shown in FIG. 4 . The spatial magnetic field gradient B0 used for imaging is only present during MRI scanning In practice, it is not impossible, but it is very difficult to translate this highly technical information into a positioning guidance. The operator has to figure out by himself how to correctly position the patient 27 on the table and correctly move the patient 27 into the gantry 10. A field plot as shown in FIG. 4 does not contain any positioning information such as “The implant 25 must not come closer than 50 centimeters to the edge of the patient table,” for example. This means that there is a need for supporting the operator to assist her in inserting the patient 27 into the MR scanner 11.

Therefore, this disclosure provides different embodiments for determining the trajectory 23 for the implant 25 so that the implant 25 does not enter any critical regions 21. In FIG. 5 , a schematic overview over the data processing apparatus 100 is shown. FIG. 5 shows a three-dimensional camera 17, and two different trajectories 23 for two different respective implants 25. Furthermore, the patient 27 is approximated by the avatar 22. A first sensor 18 can measure a size of the avatar 22 or patient 27. A second sensor 19 can measure a weight. The second sensor can be integrated in the patient table 13.

Although in FIG. 5 the avatar 22 is presented two-dimensionally, it is possible to gather a three-dimensional avatar model by the three-dimensional camera 17. The MR scanner 11 can comprise an interface 30 for transmitting necessary data to determine the correct trajectory 23. A three-dimensional camera 17 can provide the avatar 22 of the patient 27 during positioning of the patient 27 on the table 13. The avatar 22 represents the body dimensions of the patient 27, and the data processing apparatus or the control unit 15 can calculate or determine the relative position of the avatar 22 to the patient table 13 and hence to the complete scanner 11. If the position of the implants 25 within the avatar 22 are known, the control unit 15 can determine all positions of the implants 25 during inserting the patient 27 into the MR scanner 11.

In FIG. 5 , two arrows close to the implants 25 indicate a direction of inserting the patient 27 into the scanner 11. Using the interface 30, the control unit 15 is configured to receive all necessary data sets and information for determining the trajectories 23 of the implants 25. Together with the magnetic field gradient data set, the control unit 15 is configured to determine all critical regions 21 where the implants 25 would reach an area where the magnetic field gradient value exceeds a given threshold value. The threshold value is usually given or provided by the manufacturer of the implant 25. Since the control unit 15 is configured to determine an avatar pose from the patient 27 at a starting point 23 s, the control unit 15 is also configured to recalculate the trajectories 23 if the pose of the patient 27 is changed. For example, in case of FIG. 5 , the operator immediately can see that the implant 25 nearby the hand of the patient 27 will enter a critical region 21. Since the control unit 15 may visualize this trajectory 23, it is easy to see that the patient 27 should move his right arm close to the torso.

In case of FIG. 5 , the data processing apparatus 100 includes the three-dimensional camera 17. This three-dimensional camera 17 can create the avatar 22. The two different implants 25 are at different positions within the avatar 22. In case of FIG. 5 , the patient is lying on the patient table 13, and the patient 27 has a pacemaker as one implant 25 and another implant 25 near his right hand. With the help of the received information, the control unit 15 can calculate the trajectories 23 for these two implants. This means that two different trajectories 23 are calculated, and the control unit 15 is configured to combine the trajectories 23 with the magnetic field gradient data set provided by the MR scanner 11. Therefore, the control unit 15 is configured to calculate the critical region 21 for the implant 25 of the patient's hand. For this implant in the patient's hand 25, the control unit 15 of the data processing apparatus 100 is configured to provide a warning signal to the operator.

Furthermore, the control unit 15 is configured to determine a different pose of the avatar 22 at the starting point 23 s that leads to another different trajectory 23 which does not enter any critical regions 21. In case of FIG. 5 , the control unit 15 can suggest to move the implant 25 of the patient's hand by a certain distance towards the center of the patient table 13. It is also possible that the control unit 15 is configured to generate an appropriate positioning instruction such as “please move the right hand near to your main body” before the patient table 13 is moved into the gantry 10. All necessary information may be collected and/or provided by the operator for the control unit 15. This information may comprise e.g. the pose of the avatar 22, localization information of the implants 25 inside the avatar 22, the provided magnetic field gradient data set of the MR scanner 11, the moving direction of the patient table 13 and/or an intended vertical movement of the implant 25, etc. The control unit 15 may be configured to provide an information signal that indicates that more information is necessary to determine the correct trajectory 23. From the given information, the control unit 15, a computer, or a microprocessor is configured to calculate the position of the at least one implant 25 relative to the patient table 13. By assuming that the table 13 moves the patient's body to the isocenter of the scanner 11, the control unit 15 is configured to calculate all positions of the implant 25 during the motion of the patient table 13. Furthermore, the control unit 15 is configured to check if any of the calculated positions has a higher spatial field gradient than the threshold value. Therefore, the control unit 15 is configured to compare the spatial field gradient values along the trajectories 23 with the corresponding threshold value.

The control unit 15 is configured to optically enhance the determined trajectories 23. For example, the control unit 15 is configured to provide three-dimensional field plots, look up tables, a two-dimensional representation as shown in FIG. 5 , or even write a mathematical function for easier positioning of the patient on the table 13. Moreover, the control unit 15 may be configured to warn the operator during inserting the patient 27 into the gantry 10 if the implant 25 would enter a critical region 21. For this purpose, the control unit 15 may provide an acoustic instruction e.g. “please move the patient 27 five centimeters to the right!” The operator can provide the control unit 15 with information regarding whether it is from the corresponding patient file. The control unit 15 may be configured to assist the patient 27 to move himself into the right position with visual cues. For this purpose, a live view of the patient's body can be provided by the camera 17 accompanied with red or green light. By means of appropriate arrows, a movement of relevant parts of the body can be indicated. This can assist the patient 27 or the operator in positioning the patient 27 in the right pose that leads to the desired trajectory 23 of the implant 25.

The control unit 15 may be configured to refine its prediction by knowing how far the avatar 22 is moved into the scanner 11. For example, if the patient 27 is positioned with his feet first and receives an examination of the ankle, any implant 25 in the brain of the patient 27 will stay far away from the isocenter. In this case, it is possible that the implant 25 is exposed to smaller spatial field gradient values B0 than if it had been moved into the isocenter. In this case, the implant 25 of the brain does not even reach any critical region 21 since the end point 24 would stop before reaching the critical region 21. The control unit 15 may utilize images from other imaging techniques to provide a fused data set for determining the desired trajectory 23. Therefore, the control unit 15 can use data from CT-scans, X-ray scans, or previous MR examinations which are typically needed to screen for magnetic resonance imaging anyway.

By means of the three-dimensional camera 17, a three-dimensional avatar 22 can be created. The control unit 15 may be configured to predict the trajectory 23 that is the path of the implant 25 while moving the patient 27 into the MR scanner 11. This information can be combined with information about the spatial field gradients B0 of the scanner 11. Therefore, the control unit 15 is able to predict whether the implant 25 reaches or touches critical regions 21 where a magnetic field gradient value B0 exceeds the corresponding threshold value. In such situations, the control unit 15 or the data processing apparatus 100 can warn the operator or even derive guidance for enhanced positioning. In the best case, the control unit 15 can assist the operator in avoiding any violation of the limits with regard to the spatial field gradients and in combination with the implants 25. Overall, this disclosure provides different embodiments that can help the operator to position the patient 27 and thus the implant 25 correctly. This is achieved by determining the correct trajectory 23 that does not enter any critical region 21. This correct trajectory 23 is influenced by different poses of the avatar 22 that represent the pose of the patient 27.

FIG. 6 shows a possible flow diagram concerning a method for determining a trajectory 23 for inserting a patient 27 into the MR scanner 11. In a first step a) the avatar 22 is provided, which in this example consists of several ellipses that represent the head, the arms, the torso and the legs. The avatar 22 represents specific body dimensions of the predetermined patient 27. As indicated in FIG. 6 the avatar 22 preferably includes location information with regard to the at least one implant 25. In the case of FIG. 6 , the implant 25 is a pacemaker.

In a next step b) the spatial magnetic field gradient B0 data set is provided with regards to the MR scanner 11.

In a next step c) the avatar pose is defined at the starting point 23 s of the trajectory 23. Furthermore, the course of the trajectory 23 is also defined for inserting the patient 27 into the MR scanner 11. This means that steps a) to c) are preferably designed to gather all information needed for determining the trajectory 23 to insert the patient 27 into the MR scanner 11. In FIG. 6 it is indicated that the spatial magnetic field gradient data set B0 and the starting point 23 s, as well as the trajectory 23, can be input data with respect to the relevant steps.

In a next step d) several points on the trajectory 23 of the corresponding magnetic field value B0 and/or its gradient value are determined. This means that in step d) may be e.g. based on the input data in steps a) to c) in which any suitable type of calculating, determining, or outputting function is performed. Step d) can be regarded as fusing step, in which the trajectory 23 is fused with the magnetic field values B0. In this case, several trajectory points 23 together with their corresponding magnetic field values B0 are calculated or determined. This may e.g. be achieved by combining the spatial magnetic field gradient B0 data set with the avatar pose.

In a next step e) another trajectory 23 can be determined and/or the trajectory 23 can be adapted. This is also true concerning the avatar 22 and the pose of the avatar 22.

In FIG. 6 it is indicated that the avatar 22 in step a) has another pose than in step e). In step a) the head of the avatar is directed to the right, and in step e) the head of the avatar 22 rather faces upwards. This may represent another pose concerning the avatar 22. Of course the trajectory 23, the starting point 23 s, of the trajectory 23, and the pose of the avatar 22 can be changed or adapted as mentioned or explained in all embodiments of this disclosure. A new trajectory, starting point 23 s, and/or pose of the avatar 22 may be determined and/or adapted in a way so that the at least one implant 25 only passes regions within the MR scanner 11 that are below their predetermined threshold value concerning the magnetic field gradient B0, as discussed herein.

In a next step f) the information signal can be generated. The information signal may be indicated as an exclamation point or as an “OK” signal. Of course, the information signal can be more complex. For example, the information signal can be an animation with arrows that may show on a monitor how the avatar 22 shall be changed with regard to its pose. If the information signal is not “OK”, the method can be carried out again and/or the method can be turned into a regulation. In this case, it is possible that the method starts again with step a). It is also possible that the method starts at another step, for instance step b), step c) or step d). The method may be performed any suitable number of times as required until in step f) the “OK” signal is outputted.

FIG. 6 is only one exemplary embodiment that shows one possible way of realizing the disclosure. All explanations with regard to the other figures can be analogously implemented in the procedure with regards to FIG. 6 . Overall, this disclosure shows how a patient 27 can be inserted safely into the MR scanner 11. This is especially relevant if the patient 27 contains the implant 25, in this case a pacemaker. In this way, a more convenient examination can be provided for the patient 27.

The various components described herein may be referred to as “units” or “apparatuses”. Such components may be implemented via any suitable combination of hardware and/or software components as applicable and/or known to achieve the intended respective functionality. This may include mechanical and/or electrical components, processors, processing circuitry, or other suitable hardware components, in addition to or instead of those discussed herein. Such components may be configured to operate independently, or configured to execute instructions or computer programs that are stored on a suitable computer readable medium. Regardless of the particular implementation, such devices, units, and facilities, as applicable and relevant, may alternatively be referred to herein as “circuitry,” “processors,” or “processing circuitry,” or alternatively as noted herein. 

What is claimed is:
 1. A method for determining a trajectory for inserting a patient into a magnetic resonance (MR) scanner, comprising: providing an avatar representing body dimensions of a patient, the avatar including location information relating to an implant identified with the patient; providing a spatial magnetic field gradient data set relating to the MR scanner; defining (i) an avatar pose at a starting point of the trajectory, and (ii) a course for the trajectory for inserting the patient into the MR scanner; determining, for several points on the trajectory, a corresponding magnetic field value and/or a corresponding gradient value using the spatial magnetic field gradient data set and the avatar pose; determining the trajectory and/or the avatar pose such that the implant passes through regions within the MR scanner having a magnetic field gradient that is less than a predetermined threshold value; and generating an information signal that indicates whether the determined trajectory leads to the implant entering regions having a magnetic field gradient exceeding the predetermined threshold value.
 2. The method according claim 1, wherein the implant is from among a plurality of implants, and wherein the avatar comprises location information of the plurality of implants, and further comprising: determining a set of separate trajectories, each one of the set of separate trajectories corresponding to one of the plurality of implants by applying, for each one of the set of separate trajectories, a separate predetermined threshold value.
 3. The method according to claim 2, further comprising: generating a warning signal when none of the set of separate trajectories results in a passage of a corresponding implant through respective regions within the MR scanner having a magnetic field gradient below the corresponding predetermined threshold value.
 4. The method according to claim 1, wherein the act of determining the trajectory comprises: applying a coordinate system with respect to the MR scanner, wherein a coordinate of the coordinate system represents an insertion depth of the patient into the MR scanner.
 5. The method according to claim 1, wherein the avatar comprises information regarding the pose of the patient, and wherein the act of determining the trajectory comprises determining the trajectory considering a maximum insertion depth of the patient into the MR scanner and the pose of the patient.
 6. The method according to claim 1, wherein the act of adapting the trajectory comprises adapting the trajectory by determining the pose of the avatar for a starting point of the trajectory using one or more images of the patient at the starting point.
 7. The method according to claim 1, wherein the act of providing the avatar comprises providing the avatar using data acquired via (i) a camera, (ii) a first sensor configured to measure dimensions of the patient, and/or (iii) a second sensor configured to measure a weight of the patient.
 8. The method according to claim 1, wherein the act of providing the avatar comprises providing a three-dimensional (3D) avatar using data acquired via (i) a 3D camera, (ii) a magnetic resonance imaging (MRI) scan, (iii) a magnetic resonance tomography (MRT) scan, and/or (iv) a computerized tomography (CT) scan.
 9. The method according to claim 8, wherein the act of determining the trajectory comprises: determining a three-dimensional trajectory in which a point corresponding to the implant changes in a vertical direction along the trajectory, wherein the vertical direction is perpendicular to an insertion direction of the patient into the MR scanner.
 10. The method according to claim 1, wherein the avatar is fused with data relating to the implant, and wherein the data is provided by (i) an X-ray photograph, (ii) a magnetic resonance imaging (MRI) image, and/or (iii) a computerized tomography (CT) image.
 11. The method according to claim 1, wherein the avatar is fused with data relating to the implant, and wherein the avatar is approximated by a rectangular model.
 12. The method according to claim 1, further comprising: fusing the spatial magnetic field gradient data set and the trajectory to provide a magnetic path data set.
 13. The method according to claim 1, further comprising: approximating the location information of the implant as one or more planar areas or volumes which completely contain the implant.
 14. The method according to claim 1, further comprising: determining positioning instructions for adapting the trajectory based upon the act of determining the trajectory and/or determining the avatar pose.
 15. The method according to claim 1, wherein the implant is from among a plurality of implants, and further comprising: determining a set of separate trajectories, each one of the set of separate trajectories corresponding to one of the plurality of implants, and each one of the set of separate trajectories relating to a course of a respective implant.
 16. The method according to claim 1, wherein the trajectory of the implant is determined based upon patient body dimensions represented via the avatar and gantry dimensions of the MR scanner.
 17. A non-transitory computer-readable medium having instructions stored thereon that, when executed via processing circuitry, cause the processing circuitry to determine a trajectory for inserting a patient into a magnetic resonance (MR) scanner by: providing an avatar representing body dimensions of a patient, the avatar including location information relating to an implant identified with the patient; providing a spatial magnetic field gradient data set relating to the MR scanner; defining (i) an avatar pose at a starting point of the trajectory, and (ii) a course for the trajectory for inserting the patient into the MR scanner; determining, for several points on the trajectory, a corresponding magnetic field value and/or a corresponding gradient value using the spatial magnetic field gradient data set and the avatar pose; determining the trajectory and/or the avatar pose such that the implant passes through regions within the MR scanner having a magnetic field gradient that is less than a predetermined threshold value; and generating an information signal that indicates whether the determined trajectory leads to the implant entering regions having a magnetic field gradient exceeding the predetermined threshold value.
 18. A data processing apparatus, comprising: a magnetic resonance (MR) scanner comprising an insertion tool configured to insert a patient into the MR scanner; an interface configured to receive data identified with an avatar that represents body dimensions of the patient, the avatar including (i) location information relating to an implant identified with the patient, and (ii) a spatial magnetic field gradient data set relating to the MR scanner; and control circuitry configured to determine a trajectory for inserting the patient into the magnetic resonance (MR) scanner by: defining (i) an avatar pose at a starting point of the trajectory, and (ii) a course for the trajectory for inserting the patient into the MR scanner; determining, for several points on the trajectory, a corresponding magnetic field value and/or a corresponding gradient value using the spatial magnetic field gradient data set and the avatar pose; determining the trajectory and/or the avatar pose such that the implant passes through regions within the MR scanner having a magnetic field gradient that is less than a predetermined threshold value; and generating an information signal that indicates whether the determined trajectory leads to the implant entering regions having a magnetic field gradient exceeding the predetermined threshold value.
 19. The data processing apparatus according to claim 18, wherein the MR scanner further comprises a camera, and wherein the control circuitry is further configured to utilize a detected movement inside the MR scanner for determining and/or evaluating the trajectory.
 20. The data processing apparatus according to claim 18, wherein the MR scanner further comprises a lifting device configured to lift and/or lower at least a part of the patient's body to provide vertical movement of the implant. 